HVAC Repair Tips


If your AC is not cooling and upon inspection, you see that the condenser unit or the evaporator coil in the air handler is frozen, may need the help of an air conditioner repair service for finding out the cause of the problem. If you want to fix the problems yourself, here’s what you should know about the causes and fixes of an iced-up AC unit.

How Does Your AC Unit Cools Your House?

Before we go ahead with the reasons and fixes for an AC unit freezing up, an understanding of the working of an air conditioner will aid you in making sense of the causes of this problem.

The refrigerant flows between the condenser coils and the evaporator coils for cooling. Condenser coils are in the condenser unit while evaporator coils are located in the air handling unit.

Warm air from your house is flown to the evaporator coils where cool refrigerant in the evaporator coils cools the warm air. The cool air is blown into the house. Due to this, the refrigerant becomes warm and flows to the condenser coils where the heat is expelled outside using the condenser fan.

Causes Of An AC Unit Icing Up

Dirty Air Filters

The first thing to check if your condenser unit or evaporator coils are freezing up is the air filters. Dirty air filters lead to ice on air conditioner coils. The ducts of an HVAC system have air filters to block dust and debris from getting into the system and causing problems.

When the air filters become clogged with excessive dust on them, AC can’t provide enough warm air from indoors to the evaporator coils for cooling. When there isn’t warm air or less warm air to cool, the cold refrigerant in the evaporator coils doesn’t become warm and freeze the coils.

Leaks Or Blockages In The Air Ducts

Dirty air filters cause poor airflow. However, other factors can cause it as well like leaks or blockages in the ductwork. Your AC requires a constant flow of air so the cooling process happens. If the AC is set to cooling and there is a blockage or leak in the vents, the lack of enough air will lead to condensation on the coils which will then freeze the coils.

Dirty Coils

We mentioned above that airflow is essential for cooling and the AC coils will freeze if there is insufficient airflow. However, even if the airflow is optimum, if the coils themselves have a thick layer of dust buildup on them, it will hinder the heat exchange process. So, the warm air from the house won’t be cool properly or at all by the refrigerant in the coils. In turn, the coils will freeze up.

Clogged Condensate Lines

Evaporator coils also absorb moisture from the warm air when it flows through them. This moisture is directed to the drain line that flows this moisture to a floor drain outside the house or in the bathroom.

If the condensate lines become blocked, water will accumulate in the drain line and flows back to the evaporator coils. Due to the cold refrigerant in the coils, the moisture will turn into ice and freeze up the coils.

Damaged Blower Fan Or Fan Motor

The blower fan allows air to flow on the coils. The coils cool the air due to the cool refrigerant in them. If the blower fan is damaged or the motor of the fan is malfunctioning, there won’t be enough warm air flowing to the coils for cooling. In turn, the AC won’t cool and the evaporator coils will freeze up.

Low Refrigerant Levels

When the refrigerant levels are low leads to less pressure in the AC lines leads to the freezing up of the coils.

How To Fix An AC That Is Freezing Up?

Turn On The Fan Of The AC

You can defrost your AC by using the fan of the unit. First off, turn off the AC using your thermostat to stop the cooling. After this, turn on the fan. Make sure that only the fan is on and the cooling is off.

Now, all you need to do is wait while the fan melts the ice on your AC coils. It can from a few hours to an entire day.

Replace The Air Filters

Check the air filters and clean them. If they are disposable air filters, replace them. And make sure to clean or replace your air filters every 3 months. However, if you use your AC condition more than normal, replace the air filters every 2 months.

Make sure to buy air filters of the correct type and size for optimum airflow. Note down the model’s name of the AC and ask the salesman of the AC components to show you the air filters recommended by the manufacturer. You can also research online before going to a shop.

Inspect The Air Ducts For Blockages And Leaks

Inspect the supply and return air vents for blockages like furniture or curtain blocking them. Moreover, open the vents and look for debris or anything else blocking the air from flowing in the vents. Plus, consult an expert for inspecting the air ducts for leaks and blockages thoroughly.

Clean The Evaporator And Condenser Coil

You should clean the coils of your AC to remove the buildup of dust from them and allow the heat exchange process. You can clean the coils yourself with a water hose, however, some homeowners have damaged the coils by using too powerful water pressure or a harsh cleaning brush. So, it’s better to let an AC technician clean the coils along with other components of your HVAC system.

Clean The Drain Pan And Drain Lines Of Your AC

You can clean the drain lines of your air conditioner by flushing it with a solution of hot water, white vinegar, and liquid bleach. Pour it into the pipes and let it sit for 30 minutes. Clean the pipes again by flushing hot water.

You can also use a wet/dry vacuum for sucking out debris from the drain line. Remove the filter of the vacuum before using it to avoid damage to the vacuum filter.

Check The Blower Fan

You should look for something obstructing the fan from rotating properly. After cleaning the fan, inspect the fan for damages. If the fan doesn’t work or doesn’t blow enough air, the fan motor may be blown. Have a professional AC expert inspect the fan motor of your AC and repair or replace it.

Inspect The AC System For Leaks

Low refrigerant levels lead to frozen coils. The refrigerant levels usually go low due to a leak so hire an expert for a complete inspection of the system for leaks before filling the refrigerant again. Because if the refrigerant is filled without fixing the leaks, the same problem will occur again soon. Furthermore, if your AC is too old, you should replace it.


Freezing up of the AC system shows that there is a problem to fix. You should check the air filter and the vents for blockages. If they are fine, then go ahead and consult HVAC repair services Vienna VA who can carry out an inspection of the unit to find out the cause of the coils freezing up and then fix it.


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